\newcommand{\N}{\ensuremath{N}}
\newcommand{\Xs}{\ensuremath\mathcal{X}}
\newcommand{\xs}{\ensuremath x}
\newcommand{\Zs}{\ensuremath\mathcal{Z}} % Sector-level z
\DeclareMathOperator{\var}{var} % variance
\DeclareMathOperator{\se}{se} % variance
